A week ago I watched Tony Northrup’s tutorial on how to create fake background blur video, that made me want to share a way, how I do it.
I am not saying, that this way is better, because it has some problems, but it is quite different and to some of you it will learn something new.
Here, you can see before and after.
Before I start the tutorial, I want to explain, where this technique comes from and how does it work. If you don’t care – you can skip straight to tutorial.
This blurring technique is using something called z-depth pass. It is really old technique, that is used in composting of 3d computer graphics. Basically, it allows to render 3D scene without depth of field blur, then add depth of field as part of post-processing.
Here is a quick video, that shows this workflow:
Now, knowing how z-depth pass works, you don’t have to be rocket surgeon, to figure out, that theoretically, it is possible to do the same thing with photographs in Photoshop.
So, here’s how to create fake depth of field in Photoshop, by creating z-depth pass.
Here is a quick time-lapse, through the entire process:
The easiest technique, to paint correct depth information of each object, is to sample color of base gradient at where the object is touching the base. Then, use this color, to paint in the object. In my case, I used clone stamp tool, to sample the base and paint in all the letters.
When the most tedious part of this process is done, let’s get to the fun part!
Open: Filter>Blur>Lens Blur…
A new window with the Lens Blur tool will pop up.
To use previously created z-depth layer – change Depth Map Source to Layer Mask.
Now, you can tweak blur amount and look with Iris parameters. To focus, on specific area, you can left-click on desired point on image, or play around with Blur Focal Distance slider.
Now, let’s talk about disadvantages and issues of this technique. Like I mentioned in the beginning, this technique requires really sharp and large images. This is because object masks need to be as sharp as possible and they have to overlap perfectly with photograph. This can be quite tedious process. Although I used Brush tool, for masking – it is better to use Pencil tool, without anti-aliasing, to have even sharper results.
Next, even with perfectly sharp and aligned z-depth pass, you will still encounter some artifacts, around the edges of objects. That can be corrected simply, by blurring these edges with Blur brush, after applying Lens Blur tool.
That is pretty much it!
Hope you enjoyed this tutorial.
Questions and comments below.